1. Field of the Invention
The present invention relates to making fire retardant materials. More particularly, the present invention relates to making fire retardant insulation. Still more particularly, the present invention relates to insulation made with cellulosic material. Further, the present invention relates to a method of making cellulosic insulation using a combination of virgin wood fiber feedstock and/or de-inked and/or re-pulped recycled feedstock.
2. Description of the Prior Art
Insulation is widely used for the purpose of passive thermal control in a broad range of applications, with building insulation being a particularly substantial application. Inorganic fiberglass has been the most common type of material used to make insulation. Fiberglass insulation is provided in blanket and blown fiber form, with the thickness of the blanket or the blown fiber fill determinative of insulative effectiveness.
Concerns over the in-situ (installed) effective performance of fiberglass as well as the product's limited fire retardant characteristics and environmental characteristics, which are now regulated under the Federal National Toxicological standards, have raised public and governmental concerns over its continued use as a thermal insulation product. Organic cellulosic insulation has been considered as one type of alternative to fiberglass and can be desirable for that purpose, particularly in regard to its environmental suitability and thermal efficiency. Currently, cellulosic insulation is made from recycled feedstock, with recycled newsprint being the primary feedstock. Other types of materials have been considered in order to increase the volume of available feedstock, such as cardboard, wood construction debris and the like.
Cellulose insulation is made in part using existing papermaking machinery and methods. Specifically, cellulose feedstock in the form of used paper, ordinarily in the form of printed newspaper, is ground or otherwise mechanically made into small pieces. In order to ensure that the cellulosic insulation conforms to fire retardant standards, the pieces are mixed and mashed together with a fire retardant chemical, which is usually a boron-based chemical in powder (i.e., solid) form that is not particularly effective at adhering to cellulose fibers. The chemical used tends to be either boric acid or borax, or an amalgamation of the two (which will be referred to herein as borate). The treated pieces may then optionally be fluffed to reduce its overall bulk density and improve its suitability for application.
Cellulosic insulation has not been widely adopted as a suitable alternative to fiberglass insulation for several reasons. First, the cost of the fabrication method mentioned above is too high to make it economically competitive. Second, the conventional recycled material used as feedstock is not adequate to produce enough material to meet market demand as a replacement for fiberglass. In addition, the method of converting various types of recycled feedstock can significantly affect the processing cost. Third, the method of joining the fire retardant material to the cellulose pieces requires the use of a considerable amount of the treatment material, in the case of powdered treatment material, such as the most commonly used pulverized borate, and the poor adhesion between the two materials.
U.S. Pat. Nos. 5,534,301 and 6,025,027 to Shutt and U.S. Pat. Nos. 4,386,119 and 4,454,992 to Draganov describe the use of liquid borate as a means to reduce the amount of borate needed to cover cellulose insulation fibers. However, the processes described in those patents involve the application of the liquid borate to the fibers after they have been substantially manufactured, including through the dewatering stage. This method is of limited commercial value and may not adequately address the difficulty in joining the fire retardant chemical to the fibers.
Therefore, what is needed is a system and related method for making cellulosic insulation in a cost competitive way. What is also needed is such a system and related method that can be used with new feedstocks instead of or in addition to, conventional material (specifically, recycled newsprint). Further, what is needed is a system and related method to improve the fire retardant application method and fire retardant material retention on or in the cellulosic material.